The present invention relates to an improved sliding closure unit for selectively discharging liquid melt from a liquid melt container of the type including an outer jacket, an inner refractory lining and a pouring opening extending through such lining. This type of sliding closure unit is employed in cooperation with the melt container to selectively block and unblock the pouring opening. Such sliding closure unit includes a stationary refractory plate having therethrough a flow passage for communication with the pouring opening, a sliding refractory plate in abutting contact with the stationary refractory plate and having therethrough at least one flow passage to be selectively moved into and out of alignment with the flow passage of the stationary refractory plate, the stationary and sliding refractory plates having complementary, abutting relative sliding surfaces.
This type of sliding closure unit is extensively employed in the steel making industry and is particularly suitable therefor due to the consistency of the melt materials involved. However, the use of this type of sliding closure unit for various non-ferrous melted metals presents certain inherent difficulties. Such non-ferrous metals, particularly aluminum, become relatively highly superheated and are poured with a correspondingly high degree of fluidity. As a result, the aluminum melt penetrates easily between the sliding surfaces of the stationary refractory plate and the sliding refractory plate and into the open pores of the sliding surfaces. This disadvantage of light non-ferrous metals is much less of a problem with liquid steel due to the consistency thereof. Once the melted material has infiltrated between the refractory plates and becomes solidified thereat, further infiltration and solidification rapidly increase, and in many cases results in failure of the closure unit.